Production of mat light-sensitive photographic paper



PRODUCTION OF MAT LIGHT-SENSITIVE PHOTOGRAPHIC PAPER Filed Feb. 25, 1938 sldver lea/Male grab 2s szLZn/er halide 97 032 wax pow-tides protective Jag e? .senstve dryer supper? I kotecteLve da e? wax parh'cdea INVENTOR Judua 'Knoef'ei HIS ATTORNEYS Patented Nov. 1940 u rrEo s'rATe-s PRODUCTION OF MAT LIGHT- SENSITIVE PHOTOGBAPHIO PAPER- Julius Knoefel, Ieverkusen-Wiesdorf, Germany;

assignor, by mesne assignments, to General Amline & Film Corporation, New York-,N. Y., a corporation of Delaware Application February 25, 1938, Serial Not 192,562

, In Germany March 16,1193? 70mins.-

The present invention relates to improvements in producing mat light-sensitive photographic papers. Among matting agents for lightsensitive photographic papers starch is the best known. Starch has, however, injurious properties which render the substitution for it of another matting agent highly desirable.- The disadvantages of starch matting are associated both with the casting of the emulsion and the production of; the image. The chief disadvantage in casting is that the starch settles in the photographic emulsion, whereby 'streakiness and irregularities of all kinds 3 are unavoidable in the matting.

A further disadvantage in the casting is that the paper receiving the emulsion becomes curved and rolled up during-and after the drying process, so that the further use of it is made difllcult. In the production of the image the starch used as the matting agent has the disadvantage that the blacks of the photographic picture, especially with high degrees of matting, are grey and lack saturation, sothat theg radation of the photo- 25' graphic picture is flat.

' The aforesaid tendency of starch matted papers construction excepting that the wax particles are in the sensitive layer only; and x Figure 3 is a similar section through a similar film wherein, however, the wax particles are confined to the protective layer.

' The waxy substances hereinafter referred to generally as waxes solid at ordinary temperature do.,not settle in thephotographic emulsion and do not produce either rolling up or curvature.

In the finished picture the saturation of the 1 blacks is not disadvantageously'affected' by the addition of wax nor is there adisturbing change in the gradation of the picture. The passage of the starch into paste with corresponding damage, during the hot drying of the photographic 15 paper, need not be feared when waxy bodies are used.

' It has already been proposed to' add wax to a sensitive emulsion-layerfor the; purpose of'im I proving the mechanical properties of the layer. 20 In that proposal, however, the size of the particles of wax is to be the sameas that of the grain of the sensitive emulsion. The size of the grain of the waxy material may-be brought to that desired by suitable methods of dispersion; In the process of this inventionit is necessary to rollv up is not only a trouble in connection F that the dispersion of the wax, for instance in with the'caSting operation, but also very troublesome in the finished picture. In the usual hot drying of the starch matted picture thetendency of thestarch to. become paste gives rise to disturbing lustrous parts of the'picture.

It is one of the objects of this invention to provide aproces's for minimizing or avoiding the foregoing and other disadvantages of the starch o matting.

- Another object matting photographic papers by means ofa waxy material.

Still 'anotherobject is to provide a process ,for producing mat photographic papers by adding wax or waxy material to the light-sensitive layer or the protective .layer or both "of these, the size of, the particles 'of the added material 5 exceedingthat of the'grain ofthe light-sensitive emulsion. j

Further objects of the invention will appear from thedetailed descriptionfollowing'hereinafter when taken with the accompanying selfexplanatory drawing in winch:- 1

. Figure 1 is a section througha film in which the light-sensitive layer carries a protective layer, both the sensitive layer-and the protectlvelayer containing wax particles; 4

is the provision of a process for water, should havea sufficient stability so that the dispersion'may be mixed in any desired'proportion with the photographic emulsion without 30 flocculation of the wax, with a proportion depending on the desired matting effect.

According to" the invention dispersions of this kind can advantageously be obtained if, in the production of the aqueous dispersion of wax, both to the dispersing agent (water) and the body' to be dispersed (wax) there is added before the dispersion an emulsifying agent. The'emulsifying agents found in the market, for instance Saponin, Emulphor 0 (registered trade-mark), are. suitable; r i

The following" example illustrates the inven-- tion: w

15 grams of montana wax, 5 grams of stearic acid and 2.5 grams of Emulphor O-are melted together on the water bath. 2.5 grams of Emulphor O are dissolved in cc. of water andwhile stirring at'80 C. the molten mixture of wax is-poured into the solution. Theaqueous dispersion'of wax thus obtainedis then cooled and 50 added to the photographic emulsion. Thesize' 0f the particles in the dispersion considerably larger than that ofth'e silver-halide grain in the usual photographic paper emulsion;

Figure 2 is a tion thr u h a fllniof similar In 4 the example the montana wax and the" stearic acid may be exchanged for a ceresin wax. carnauba wax, a synthetic wax, fatty acids high molecular weight and other waxy bodies.

What I claim is:

1. -A photographic paper comprising in superimposition a paper support, a silver halide emulsion layer and a protective layer, at least one of said layers containing a wax solid at ordinary temperature, the size of the particles of said substance exceeding that of the grain of said emulsion layer. I

2. A photographic paper comprising in superimposition a paper support, a silver halide emulsion layer and a protective layer, said emulsion layer containing a wax solid at ordinary temperalayer containing a wax solid at ordinary temperature, the size of the particles of said substance exceeding that of the grain of said emulsion layer.

4. A photographic paper comprising in superimposition .a paper support, a silver halide emulsion layer and a protective layer, said emulsion layer and said protective layer containing a wax solid at ordinary temperature, the size of the particles of said substance exceeding that of the grain of said emulsion layer.

5. A photographic paper comprising in superimposition a paper support, a silver halide emulsion layer and a protective layer, at least one of said layers containing montana wax, the size of the particles of said substance exceeding that of the grain-0f said emulsion layer- 6. A photographic paper comprising in superimposition a paper support, a silver halide emulsion layer and a protective layer, at least one of said layers containing a synthetic wax, the size of the particles of said substance exceeding that of the grain of said emulsion layer. V

7. A photographic paper comprising in superimposition a paper support, a silver halide emulsion layer and a protective layer, at least one of said layers containing a fatty acid of high molecular weight, the size of the particles of said substance exceeding that of the grain of said emulsion layer.

JULIUS KNOEFEL. 

